Conventionally, a telephone service operator provides an unrestricted access by clients to voice telephone services, and shuts the service when the clients ceases to pay its invoices for the services. Since around a decade, mobile telephone service operators provide communications quota included in a package of services.
Whatever the commercial offer is, it can happen that clients are temporarily insolvable, and this causes a financial loss for the operator as well as an inhibition of the access to the telecom services, which in turn causes client dissatisfaction.
In order to limit the situations of insolvency, a known solution consists in:                either refusing potentially insolvent client when they apply for a subscription,        or obtaining a security for them,        or else obtaining a pre-payment for a credit allowing to use the services until the credit is exhausted.        
Besides, many “over the top” (OTT) communications applications have been developed over the recent years such as Skype®, Go-Text.Me®, Twitter® ou Whatsapp®. However, they all require specific identifiers and a separate subscription to a telecommunications service (cell phone subscription including data service, DSL home subscription, etc.). Such identifiers are thus not compatible with the calling numbers of the conventional telecom operators, including a country code followed by a number of digits.